chore: handle vim.validate deprecation

fix: use json parser instead of jsonc

fix: run postStartCommand on host and substitute workspace folder

fix: correctly check for nvim 0.12 before using :connect command

chore: directly define luacheck in CI

chore: run CI on `codeberg-tiny`

chore: fix stylua issues

chore: update vimdocs

docs: add `nvim_install_as_root` to README

docs: update required Neovim version

fix: fall back to containerUser when remoteUser is not defined

feat: add experimental support for :connect for attaching

fix: correctly check for stored layers to prevent neovim reinstall

fix: add missing validation for `nvim_install_as_root`

feat: add `nvim_install_as_root` option